KR20180105053A - Methods for transmitting and receiving downlink channel in s short TTI frame structure and Apparatuses thereof - Google Patents

Abstract

An embodiment of the present invention relates to operation of a terminal and a base station for transmission and reception of a downlink channel in a frame structure of a short transmission time interval (sTTI) of a 3GGP LTE/LTE-advanced system. According to an embodiment of the present invention, a method for receiving a downlink channel in a frame structure of a sTTI by a terminal comprises the following steps of: receiving information on a shorted physical downlink control channel (sPDCCH) region from the base station; and receiving the downlink channel based on the information on the sPDCCH region from the base station. The sTTI is set as two, three or seven symbols.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for transmitting and receiving a downlink channel in a frame structure having a short transmission time interval,

The present embodiment relates to the operation of a terminal and a base station for transmission and reception of a downlink channel in a short transmission time interval frame structure of a 3GPP LTE / LTE-Advanced system.

Research and discussions are under way for latency reduction in 3GPP LTE / LTE-Advanced systems. The main purpose of latency reduction is to standardize the operation of shorter transmission time intervals (hereinafter referred to as 'short TTI' or 'sTTI') to improve TCP throughput.

The frame structure of such a short transmission time interval forms a frame by 2, 3, or 7 symbol units in the existing LTE / LTE-Advanced frame structure, i.e., TTI = 1 ms = 14/12 OFDM symbols, And transmits and receives data based on a frame structure of a time interval to reduce delay and improve data throughput.

A discussion of the performance of short TTIs is underway, and discussions are underway on the feasibility, performance, and backward compatibility of TTI lengths between 0.5ms and one OFDM symbol.

Although studies on the physical layer for such a short TTI are ongoing, there is no specific procedure for transmission and reception of a downlink channel in a short TTI. Specifically, a shortened PDCCH (sPDCCH) region as a downlink control channel in a short TTI is set. Based on the information on the set sPDCCH region, sPDCCH in the short TTI and downlink data channel in the short TTI There is no specific procedure for allocating time / frequency resources to the shortened PDSCH (sPDSCH).

It is an object of the present invention to provide a specific operation method of a terminal and a base station for resource allocation and transmission / reception for sPDCCH and sPDSCH based on information on an sPDCCH region by setting an sPDCCH region in a short TTI frame structure.

According to an embodiment of the present invention, there is provided a method for receiving a downlink channel in a frame structure of a short transmission time interval (sTTI) receiving shortened PDCCH (sPDCCH) region information from a base station, and receiving a downlink channel from a base station based on information on an sPDCCH region, wherein a short transmission time interval is 2, 3, or 7 symbols.

In another embodiment, a method for transmitting a downlink channel in a frame structure of a short transmission time interval (sTTI) is provided in a shortened transmission time interval (sPDCCH) field of a short transmission time interval. , Transmitting the information on the sPDCCH region to the UE, and transmitting the downlink channel to the UE based on the information on the sPDCCH region, wherein the short transmission time interval is 2 , ≪ / RTI > three, or seven symbols.

In an exemplary embodiment of the present invention, in a UE receiving a downlink channel in a frame structure of a short transmission time interval (sTTI), information on a downlink control channel (sPDCCH, shortened PDCCH) And a controller for receiving downlink control information or downlink data from the downlink channel, wherein the downlink control information or the downlink data is detected based on information on the sPDCCH region, And the transmission time interval is set to 2, 3, or 7 symbols.

In an exemplary embodiment of the present invention, in a base station transmitting a downlink channel in a frame structure of a short transmission time interval (sTTI), information on a short control channel (sPDCCH) field of a short transmission time interval And a transmitter for transmitting the information on the sPDCCH region to the mobile station and for transmitting the downlink channel to the mobile station based on the information on the sPDCCH region, wherein the short transmission time interval is 2, 3 And the number of symbols is set to seven or seven symbols.

The embodiments described above can set up the sPDCCH region in the short TTI frame structure and provide a concrete operation method of the terminal and the base station for resource allocation and transmission and reception for the sPDCCH and sPDSCH based on the information about the sPDCCH region .

1 is a diagram illustrating processing delays and a HARQ RTT (Round Trip Time) in a BS and a UE.
2 is a diagram for explaining resource mapping per physical resource block (PRB) in one subframe.
3 is a diagram for explaining an uplink structure of a conventional (legacy) PUCCH.
4 is a diagram for explaining a configuration conceptual diagram of a conventional (legacy) PUCCH.
5 is a diagram illustrating a procedure for a UE according to an embodiment of the present invention to receive a downlink channel in a frame structure of a short transmission time interval.
FIG. 6 is a diagram illustrating a procedure for transmitting a downlink channel in a frame structure of a short transmission time interval according to an embodiment of the present invention. Referring to FIG.
7 is a diagram showing an sTTI composed of two or three symbols in the downlink.
8 is a diagram illustrating an example of sPDCCH area setting according to a time domain in the 2-symbol sTTI of the present embodiment.
FIG. 9 is a diagram illustrating an example of sPDCCH area setting according to the frequency domain in the 2-symbol sTTI of the present embodiment.
10 is a diagram showing an example of a single symbol-based sCCE configuration in the 2-symbol sTTI of the present embodiment.
11 is a diagram showing an example of a 2-symbol-based sCCE configuration in the 2-symbol sTTI of this embodiment.
12 is a diagram illustrating a method of allocating an sCCE not used in an sPDCCH region to an sPDSCH in this embodiment.
13 is a diagram illustrating a configuration of a base station according to the present embodiments.
FIG. 14 is a diagram illustrating a configuration of a user terminal according to the present embodiments.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Herein, the MTC terminal may mean a terminal supporting low cost (or low complexity) or a terminal supporting coverage enhancement. In this specification, the MTC terminal may mean a terminal supporting low cost (or low complexity) and coverage enhancement. Alternatively, the MTC terminal may refer to a terminal defined in a specific category for supporting low cost (or low complexity) and / or coverage enhancement.

In other words, the MTC terminal in this specification may mean a newly defined 3GPP Release-13 low cost (or low complexity) UE category / type for performing LTE-based MTC-related operations. Alternatively, the MTC terminal may support enhanced coverage over the existing LTE coverage or a UE category / type defined in the existing 3GPP Release-12 or lower that supports low power consumption, or a newly defined Release-13 low cost low complexity UE category / type.

The wireless communication system in the present invention is widely deployed to provide various communication services such as voice, packet data and the like. A wireless communication system includes a user equipment (UE) and a base station (BS, or eNB). The user terminal in this specification is a comprehensive concept of a terminal in wireless communication. It is a comprehensive concept which means a mobile station (MS), a user terminal (UT), an SS (User Equipment) (Subscriber Station), a wireless device, and the like.

A base station or a cell generally refers to a station that communicates with a user terminal and includes a Node-B, an evolved Node-B (eNB), a sector, a Site, a BTS A base transceiver system, an access point, a relay node, a remote radio head (RRH), a radio unit (RU), and a small cell.

That is, in the present specification, a base station or a cell has a comprehensive meaning indicating a part or function covered by BSC (Base Station Controller) in CDMA, Node-B in WCDMA, eNB in LTE or sector (site) And covers various coverage areas such as megacell, macrocell, microcell, picocell, femtocell and relay node, RRH, RU, and small cell communication range.

Since the various cells listed above exist in the base station controlling each cell, the base station can be interpreted into two meanings. i) the device itself providing a megacell, macrocell, microcell, picocell, femtocell, small cell in relation to the wireless region, or ii) indicating the wireless region itself. i indicate to the base station all devices that are controlled by the same entity or that interact to configure the wireless region as a collaboration. An eNB, an RRH, an antenna, an RU, an LPN, a point, a transmission / reception point, a transmission point, a reception point, and the like are exemplary embodiments of a base station according to a configuration method of a radio area. ii) may indicate to the base station the wireless region itself that is to receive or transmit signals from the perspective of the user terminal or from a neighboring base station.

Therefore, a base station is collectively referred to as a base station, collectively referred to as a megacell, macrocell, microcell, picocell, femtocell, small cell, RRH, antenna, RU, low power node do.

Herein, the user terminal and the base station are used in a broad sense as the two transmitting and receiving subjects used to implement the technical or technical idea described in this specification, and are not limited by a specific term or word. The user terminal and the base station are used in a broad sense as two (uplink or downlink) transmitting and receiving subjects used to implement the technology or technical idea described in the present invention, and are not limited by a specific term or word. Here, an uplink (UL, or uplink) means a method of transmitting / receiving data to / from a base station by a user terminal, and a downlink (DL or downlink) .

There are no restrictions on multiple access schemes applied to wireless communication systems. Various multiple access schemes such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), OFDM-FDMA, OFDM- Can be used. An embodiment of the present invention can be applied to asynchronous wireless communication that evolves into LTE and LTE-Advanced via GSM, WCDMA, and HSPA, and synchronous wireless communication that evolves into CDMA, CDMA-2000, and UMB. The present invention should not be construed as limited to or limited to a specific wireless communication field and should be construed as including all technical fields to which the idea of the present invention can be applied.

A TDD (Time Division Duplex) scheme in which uplink and downlink transmissions are transmitted using different time periods, or an FDD (Frequency Division Duplex) scheme in which they are transmitted using different frequencies can be used.

In systems such as LTE and LTE-advanced, a standard is constructed by configuring uplink and downlink based on a single carrier or carrier pair. The uplink and the downlink are divided into a Physical Downlink Control Channel (PDCCH), a Physical Control Format Indicator CHannel (PCFICH), a Physical Hybrid ARQ Indicator CHannel, a Physical Uplink Control CHannel (PUCCH), an Enhanced Physical Downlink Control Channel (EPDCCH) Transmits control information through the same control channel, and is configured with data channels such as PDSCH (Physical Downlink Shared CHannel) and PUSCH (Physical Uplink Shared CHannel), and transmits data.

On the other hand, control information can also be transmitted using EPDCCH (enhanced PDCCH or extended PDCCH).

In this specification, a cell refers to a component carrier having a coverage of a signal transmitted from a transmission point or a transmission point or transmission / reception point of a signal transmitted from a transmission / reception point, and a transmission / reception point itself .

The wireless communication system to which the embodiments are applied may be a coordinated multi-point transmission / reception system (CoMP system) or a coordinated multi-point transmission / reception system in which two or more transmission / reception points cooperatively transmit signals. antenna transmission system, or a cooperative multi-cell communication system. A CoMP system may include at least two multipoint transmit and receive points and terminals.

The multi-point transmission / reception point includes a base station or a macro cell (hereinafter referred to as 'eNB'), and at least one mobile station having a high transmission power or a low transmission power in a macro cell area, Lt; / RTI >

Hereinafter, a downlink refers to a communication or communication path from a multipoint transmission / reception point to a terminal, and an uplink refers to a communication or communication path from a terminal to a multiple transmission / reception point. In the downlink, a transmitter may be a part of a multipoint transmission / reception point, and a receiver may be a part of a terminal. In the uplink, the transmitter may be a part of the terminal, and the receiver may be a part of multiple transmission / reception points.

Hereinafter, a situation in which a signal is transmitted / received through a channel such as PUCCH, PUSCH, PDCCH, EPDCCH, and PDSCH is expressed as 'PUCCH, PUSCH, PDCCH, EPDCCH and PDSCH are transmitted and received'.

In the following description, an indication that a PDCCH is transmitted or received or a signal is transmitted or received via a PDCCH may be used to mean transmitting or receiving an EPDCCH or transmitting or receiving a signal through an EPDCCH.

That is, the physical downlink control channel described below may mean a PDCCH, an EPDCCH, or a PDCCH and an EPDCCH.

Also, for convenience of description, the PDCCH, which is an embodiment of the present invention, may be applied to the PDCCH, and the PDCCH may be applied to the portion described with the EPDCCH.

Meanwhile, the High Layer Signaling described below includes RRC signaling for transmitting RRC information including RRC parameters.

The eNB performs downlink transmission to the UEs. The eNB includes a physical downlink shared channel (PDSCH) as a main physical channel for unicast transmission, downlink control information such as scheduling required for reception of a PDSCH, A physical downlink control channel (PDCCH) for transmitting scheduling grant information for transmission in a Physical Uplink Shared Channel (PUSCH). Hereinafter, the transmission / reception of a signal through each channel will be described in a form in which the corresponding channel is transmitted / received.

Latency reduction

Latency reduction is under discussion. The main purpose of latency reduction is to standardize the operation of shorter transmission time intervals (hereinafter referred to as 'short TTI' or 'sTTI') to improve TCP throughput.

Potential impacts and studies are underway in the following areas.

o Evaluate the specification impact / study feasibility / performance when the TTI length is one OFDM symbol at 0.5ms considering the influence on the control signal of the reference signal and the physical layer. lengths between 0.5ms and one OFDM symbol, taking into account the impact on reference signals and physical layer control signaling)

o Compatible with the existing system, it must support the operation of the terminal prior to Rel 13 on the same carrier (back-up compatibility shall be preserved).

Delay reduction can be achieved through the following physical layer techniques. (Latency reduction can be achieved by the following physical layer techniques)

- Short transmission time interval (short TTI)

- Reduced processing time in implementation.

- New frame structure of TDD in TDD -

Further discussion on latency reduction is further discussed below.

■ Following design assumptions are considered:

   The short transmission time interval does not exceed the subframe interval (TTI spans over subframe boundary)

   o PDCCH and legacy PDSCH are used for scheduling at least for SIB and paging. (At least for SIBs and paging, PDCCH and legacy PDSCH are used for scheduling)

■ Potential impacts for the following are studied (the potential specific impacts for the followings are studied)

  o The UE is expected to receive the sPDSCH at least through downlink unicast. (UE is expected to receive a downlink unicast at the SDSCH)

    The sPDSCH indicates a PDSCH carrying data in a short TTI (sPDSCH referred PDSCH carrying data in a short TTI)

  o The UE is expected to receive the PDSCH through downlink unicast. (UE is expected to receive PDSCH for downlink unicast)

      The UE can simultaneously receive the PDSCH and the PDSCH through downlink unicast (whether a UE is expected to receive both PDSCH and PDSCH for downlink unicast simultaneously)

  o Further study of the number of short TTIs supported (the number of supported short TTIs)

■ The following design assumptions can be used in the study (following design assumptions are used for the study)

    o From the base station point of view, existing non-sTTI and sTTI can be frequency division multiplexed in the same subframe of the same carrier (From eNB perspective, existing non-sTTI and sTTI can be FDMed in the same subframe in the same carrier)

       A further study on other multiplexing methods for terminals supporting latency reduction features in existing non-sTTIs (other multiplexing method (s) with supporting latency reduction features)

■ In this study, we assume the following points (in this study, the following aspects are assumed in RAN1.)

   o Procedures related to PSS / SSS, PBCH, PCFICH, PRACH, random access, paging and SIB are not changed (PSS / SSS, PBCH, PCFICH and PRACH, Random access, SIB and Paging procedures are not modified.

■ Further discussions are made on the following aspects: (1)

  o Research is not limited to the following:

  o Design of sPUSCH DM-RS of DM-RS of sPUSCH

   (1): The same DM-RS symbol is shared among several short-TTIs in the same subframe (Alt.1: DM-RS symbol shared by multiple short-TTIs within the same subframe).

   (2) Each sPUSCH has a DM-RS. (Alt.2: DM-RS contained in each sPUSCH)

  o HARQ for sPUSCH on sPUSCH

   Whether or not to recognize asynchronous and / or synchronous HARQ (synchronous HARQ)

         o In addition to the non-CA case, the sTTI operation in PCell and SCell in the CA (sTTI operation for Pcell and / or SCells by (e) CA in addition to non-

1 is a diagram for explaining processing delays and HARQ RTT (Round Trip Time) in a Node B and a UE.

Basically, in the average down-link latency calculation, the delay can be calculated according to the following procedure.

The unidirectional delay in the user plane of LTE for the scheduled UE may consist of fixed node processing delay as shown in Figure 1 below and one TTI duration for transmission. Assuming that the processing time can be scaled by the same TTI reduction factor that maintains the same number of HARQ processes, the unidirectional delay can be calculated as follows (see Equation B.2.1 in 3GPP TR 36.912, the LTE U-plane one-way latency for a scheduled UE consists of the fixed node processing delays and 1 TTI duration for transmission, as shown in Figure A.1 below. TTI reduction keeping the same number of HARQ processes, the one way latency can be calculated as)

D = 1.5 TTI + 1 TTI + 1.5 TTI UE + n * 8 TTI (HARQ retransmissions)

    = (4 + n * 8) TTI.

If there is a retransmission of 0 or 1 and the probability of error in the first transmission is p, then the delay can be calculated as follows (Considering a typical case where there would be 0 or 1 retransmission, and assuming error probability of the first transmission to be p, the delay is given by)

D = (4 + p * 8) TTI.

So, for 0% BLER (Block Error Rate), D = 4 * TTI,

And for 10% BLER, D = 4.8 * TTI.

At the UE  Average uplink transmission delay calculation starting (Average UE  initiated UL transmission latency calculation)

It is assumed that the UE desires an uplink transmission such as a connection state, a synchronization state, and a transmission of a TCP ACK. Table 1 discloses the steps for the uplink delay and the corresponding contribution. In order to maintain consistency in the comparison between the downlink and the uplink, the eNB adds eNB processing delay after receiving the uplink data. (Step 7) (Assume UE is in connected / synchronized mode and wants to do UL transmission , to send TCP ACK. The following table shows the steps and their corresponding contribution to the UL transmission latency. To be consistent in the comparison of DL and UL, we add the eNB processing delay in the UL after the UL data is received by the eNB step 7).)

Step Description Delay One. Average delay to next SR opportunity SR periodicity / 2 2. UE sends SR 1 TTI 3. eNB decodes SR and generates scheduling grant 3 TTI 4. Transmission of scheduling grant (assumed always error free) 1 TTI 5. UE processing delay (decoding scheduling grant + L1 encoding of data) 3 TTI 6. UE sends UL transmission (1 + p * 8) TTI where p is initial BLER. 7. eNB receives and decodes the UL data 1.5 TTI

In the above table, it is assumed that the half delay of steps 1 and 4 is due to a scheduling request and the remainder is assumed for uplink data transmission. (In the table above, steps 1-4 and half delay of step 5 is assumed to be due to SR, and rest is assumed for UL data transmission shown in Table 4)

Resource mapping of short TTI < RTI ID = 0.0 >

In FIG. 2, considering the control field composed of two antenna ports and two OFDM symbols, the above resource map represents an existing resource mapping of the PRB in one subframe. In FIG. 2, the following resource map is a short TTI resource mapping considering a control field composed of two OFDM symbols to ensure backward compatibility. In the short TTI, it is assumed that the loss rate at the PHY layer is (L _legacy , eg 5% - 50%). (In Figure 2, the resource map above is the legacy resource mapping per PRB in one subframe, considering 2 Antenna ports and 2 The loss rates (L _legacy , eg 5% - 50%) are used for the OFDM symbol control field. In Figure 2, the resource map below is the short TTI resource mapping, ) of the PHY layer in short TTI duration are assumed.

Transmission block size calculation in short TTI (TBS Calculation of short TTI)

According to the above-described resource mapping and transmission block size (TBS) calculation formula, the loss rate of the PHY layer for the existing PDSCH can be calculated as follows (according to the TBS calculation formula given above , the loss rate of PHY layer for legacy PDSCH is calculated as follows:

For the different short TTI duration, the transport block size in the PDSCH of the short TTI can be calculated as shown in the following Table 2. (For different short TTI duration, the TBS of the short TTI PDSCH is calculated as the following table)

TTI Duration TBS of short TTI PDSCH (TBS _short ) 7 OFDM symbol

First time slot:

Second time slot:

2 OFDM symbol

1 OFDM symbol

existing PUCCH [Existing PUCCH ]

The UL control channel through which the UE sends a response to PDSCH reception to the BS is the PUCCH. The UE can use various formats of PUCCH format to transmit Ack / Nack and CQI information for the downlink data channel to the eNB.

In the conventional LTE / LTE-Advanced frame structure (TTI = 1 ms = 14 OFDM symbols (Normal CP) / 12 OFDM symbols (Extended CP)), slot based PUCCH hopping can be performed as shown in FIG. This PUSCH hopping increases the frequency diversity of the PUCCH and consequently increases the coverage of the PUCCH. This is because basically the same signal or one information sequence is transmitted through different frequency bands, so that there is a gain to obtain diversity.

In transmitting the A / N (Ack / Nack) from the existing PUCCH, the resource allocation is applied by OCC (spreading) + CS (cyclic shift) on the basis of format 1a and 1b. As shown in FIG. 4, the existing PUCCH is set to 3 symbols RS and 4 symbols A / N on a slot basis.

In the present invention, consideration is given to the CS-based A / N multiplexing resource allocation of the Zadoff-Chu (ZC) sequence excluding the existing OCC considering that the number of symbols of the sPUCCH is reduced. Unlike the existing structure, OCC spreading is not used at this time.

에서 정의되는 cyclic shift 값으로 정의될 수 있다.The ZC sequence is basically the RS

And a cyclic shift value defined by the following equation.

In this embodiment, the following basic structure is assumed for the sPUCCH A / N configuration in which OCC is excluded.

Here, the PUCCH format 1a / b performs dynamic resource allocation. Basically, the PUCCH format 1a / b performs the same dynamic allocation as shown in Equation 2 based on the CCE index of the scheduled PDCCH.

은 하향 자원 할당에 사용된 햐향링크 제어 정보(DCI) 전송에 사용된 PDCCH의 가장 낮은 CCE 인덱스(lowest CCE index)인

와 상위 레이어에서 전송되는

에 의해서 결정된다. 여기에서

은 결국 PUCCH format 1a/1b가 다른 PUCCH format 2/3/4 등과 분리될 수 있도록 설정된 일종의 shift 값을 의미한다.Here, the PUCCH resource index for Ack / Nack

(Lowest CCE index) of the PDCCH used for downlink control information (DCI) transmission used for downlink resource allocation

And the upper layer

. From here

Refers to a kind of shift value set so that the PUCCH format 1a / 1b can be separated from other PUCCH format 2/3/4 and the like.

The following are additional agreements regarding the recent sTTI.

S Support for transmission duration based on 2-symbol sTTI and 1-slot sTTI for sPDSCH / sPDCCH (Specify support for a transmission duration based on 2-symbol sTTI and 1-slot sTTI for sPDSCH / sPDCCH)

4) Set the support for 2-symbol sTTI, 4-symbol sTTI, and 1-slot sTTI-based transmission durations for sPUCCH / sPUSCH (Specify support for 2-symbol sTTI, 4-symbol sTTI, and 1-slot sTTI for sPUCCH / sPUSCH)

   o Down-selection is not precluded

■ Investigate the impact of channel state information on feedback and processing time and, if necessary, determine the necessary corrections (CSI feedback and processing time,

o Minimum timing n + 3 for FS1, 2 and 3 is supported only for UEs capable of shortening the HARQ processing time for the UL grant and DL data for uplink data (For FS1,2 & 3, a minimum timing n + 3 is supported for UL grant to UL data and DL data to DL HARQ for UEs capable of operating with reduced processing time only:

The maximum TA is reduced to x ms, where x is less than or equal to 0.33 ms (A maximum is reduced to x ms, where x <= 0.33 ms (exact values derived from the detailed study)

   o At least when scheduled (PDCCH)

    A new DL HARQ and uplink scheduling timing relationship is defined for FS2 (For FS2, new DL HARQ and UL scheduling timing relationships will be defined)

o Further detailed study (Details FFS)

    o Additional Studies (FFS)

    o Possible minimum timing of n + 2 TTI (n + 2 TTI)

        o In this case, a further study on max TA (FFS max TA in this case)

        o Additional constraints on when the reduced processing time of n + 2 TTIs can be applied (FFS what other restrictions (if any) on when reduced processing times of n + 2 could be applied)

        o Possibility of scheduling by EPDCCH.

The reduced processing time can be set by the RRC to the UE (Reduced processing time (s) are RRC configured for the UE).

o A mechanism for dynamic fallback to legacy processing timings (n + 4) is supported for existing processing timing (n + 4)

In the case of the sPDSCH based on the CRS-based transmission scheme, the maximum number of supported layers is 4. (For the PDSCH based on a CRS based transmission scheme, the maximum number of supported layers is 4)

 In the case of the sPDSCH based on the DM-RS based transmission scheme, it may be downselected from among the following options. (For SDSCH based on a DM-RS based transmission scheme,

The number of supported maximum layers is 2 (the maximum number of supported layers is 2)

The number of supported maximum layers is 4 (the maximum number of supported layers is 4)

- the maximum number of supported layers is 8

 For the sPDSCH based on the DM-RS based transmission scheme, a detailed study on the recommendation to increase the PRB bundle size compared to the PDSCH for the sTTI length shorter than at least 1-slot (FFS for PDSCH based on a DM- RS based transmission scheme is recommended for increased PRB bundling size compared to PDSCH for at least sTTI lengths shorter than 1-slot)

The embodiments described below can be applied to a terminal, a base station, and a core network entity (MME) using all mobile communication technologies. For example, the present embodiments can be applied not only to mobile communication terminals to which LTE technology is applied but also to next generation mobile communication (5G mobile communication, New-RAT) terminals, base stations, and access and mobility functions (AMFs). For convenience of explanation, the base station may denote an eNB of an LTE / E-UTRAN or a base station (CU, DU, or CU and DU) in a 5G wireless network in which a CU (Central Unit) An entity implemented as a single logical entity), or gNB.

In addition, the general transmission time interval or the existing / legacy time interval described in this embodiment means a subframe time interval of 1 ms used in the conventional LTE / LTE-Advanced. That is, in the conventional LTE / LTE-Advanced, since the time interval of one subframe is 1 ms and 14 symbols (in case of Normal CP) or 12 symbols (in case of Extended CP), the time interval is 14 symbols or 12 It can be a symbol. Therefore, in the following embodiments, existing / legacy or generic may refer to a conventional LTE / LTE-Advanced system with a sub-frame of 1 ms.

In addition, the type of the short transmission time interval described in this embodiment is for distinguishing the symbol length of the TTI in a short transmission time interval. Specifically, the symbol length means the number of symbols constituting one short transmission time interval do. In this embodiment, the short transmission time interval may be set to two, three, or seven symbols.

In addition, the symbol described in this embodiment means an OFDM symbol, and the symbol may be an RS symbol or a data symbol. A data symbol means an OFDM symbol storing information.

In addition, the downlink channel described in this embodiment may be a downlink control channel or a downlink data channel. In a frame structure of a short transmission time interval (hereinafter referred to as a short TTI or sTTI), the downlink channel is divided into a downlink control channel (sPDCCH) of a short transmission time interval or a downlink data channel (sPDSCH ).

5 is a diagram illustrating a procedure for a UE according to an embodiment of the present invention to receive a downlink channel in a frame structure of a short transmission time interval.

Referring to FIG. 5, the UE can receive information on a shortened PDCCH (shortened PDCCH) region of a short transmission time interval from a base station (S500).

The sPDCCH field is an area in which a sPDCCH can be transmitted in a short TTI. The sPDCCH region is configured in units of symbols for time, and is configured in RB (Resource Block) units for frequency. In this embodiment, the sPDCCH region may be configured based on a single symbol or a plurality of symbols, and may be composed of one or two symbols, for example.

The terminal can receive information on the sPDCCH region from the base station through RRC signaling.

Also, the UE can receive the downlink channel from the Node B based on the information on the sPDCCH region received from the Node B (S510).

The sPDCCH field indicates an area in which the sPDCCH can be transmitted, but not all the resources belonging to the sPDCCH field have to be used for the sPDCCH. At this time, the resources not used for the sPDCCH among the resources belonging to the sPDCCH region can be reused for the sPDSCH transmission without leaving the unused state. That is, the sPDCCH and the sPDSCH can be multiplexed in the sPDCCH region.

When the sPDCCH and the sPDSCH are multiplexed in the sPDCCH region, information is required to indicate which one of the resources of the sPDCCH region is sPDCCH and which resource is the sPDSCH when the UE receives the downlink channel from the base station. That is, the UE must receive information indicating a resource not used in the sPDCCH among the resources belonging to the sPDCCH area. This information can be represented by an arbitrary number of bits. The UE can receive information indicating the resources not used for the sPDCCH among the resources belonging to the sPDCCH region from the base station through the DCI.

FIG. 6 is a diagram illustrating a procedure for transmitting a downlink channel in a frame structure of a short transmission time interval according to an embodiment of the present invention. Referring to FIG.

Referring to FIG. 6, the base station can set information on the sPDCCH region (S600).

As described above with reference to FIG. 5, the sPDCCH field indicates an area in which the sPDCCH can be transmitted in a short TTI. The sPDCCH region may be configured in symbol units for time and the RB (Resource Block) unit for frequencies. In this embodiment, the sPDCCH region may be configured based on a single symbol or a plurality of symbols, and may be composed of one or two symbols, for example.

The base station can transmit information on the set sPDCCH region to the mobile station (S610). For example, the base station can transmit information on the sPDCCH region to the mobile station through RRC signaling.

The base station can transmit the downlink channel to the mobile station based on the information of the sPDCCH area (S620).

Since all resources belonging to the sPDCCH region need not be used for the sPDCCH as described above with reference to FIG. 5, resources not used for the sPDCCH among resources belonging to the sPDCCH region can be reused for transmission of the sPDSCH without leaving the unused state. That is, the sPDCCH and the sPDSCH can be multiplexed in the sPDCCH region.

When the sPDCCH and the sPDSCH are multiplexed in the sPDCCH region, information for indicating which one of the resources of the sPDCCH region is the sPDCCH and which resource is the sPDSCH is required. That is, the BS must transmit to the UE information indicating a resource not used for the sPDCCH among the resources belonging to the sPDCCH area. At this time, as described above, the base station can transmit information indicating a resource not used for the sPDCCH among the resources belonging to the sPDCCH region to the mobile station through the DCI.

Hereinafter, various embodiments of a method for transmitting and receiving a downlink channel in a frame structure of a short transmission time interval between a terminal and a base station will be described in detail. The embodiments described below may be used individually or in any combination.

First, the sTTI structure has a structure similar to DL and UL based on 2-symbol and 7-symbol. The current 2-symbol, 7-symbol sTTI structure is determined, and the slot boundary of each subframe is maintained. For example, in a 2-symbol sTTI structure, an up / down sTTI may exist as shown in FIG.

Referring to FIG. 7, in a two-symbol sTTI, each sTTI is basically composed of two symbols. However, if all of the sTTIs are composed of only two symbols, one symbol is left when dividing the seven odd symbols into two, so that there is a problem that the slot boundary of the subframe composed of seven symbols can not be maintained. Therefore, sTTI0 and sTTI5, which are one of the sTTIs in the slot, may be composed of three symbols in order to align the slot boundaries of each subframe. That is, in a 2-symbol sTTI, each sTTI may be composed of 2 symbols or 3 symbols.

On the other hand, in 7-symbol sTTI, each sTTI is composed of 7 symbols, which is the same length as a slot of a legacy subframe.

In this embodiment, a multiplexing method between a specific control channel (sPDCCH) and a data channel (sPDSCH) will be described based on the above description.

Example  One. sTTI  The control channel is x symbol  Based sPDCCH  Set up and send a zone

In this embodiment, it is assumed that the sPDCCH region of the sTTI is basically set semi-static through RRC signaling. Therefore, the sPDCCH area in the sTTI setting area may exist separately.

When setting the sPDCCH area to RRC, the following considerations can be considered. However, some or all of the sPDCCH area setting information described below can be transmitted by dynamic signaling through DL grant. Specifically, when the two-level DCI is applied, the sPDCCH area configuration information can be transmitted to each of the terminals through DCI2 (control information transmitted through the Legacy PDCCH).

- Set the number of symbols x in the sPDCCH area

In this embodiment, a single symbol-based sPDCCH setting is possible, and a multiple symbol-based sPDCCH setting is also possible.

Referring to FIG. 8, in the case of a 2-symbol sTTI, a sPDCCH region can be set to one symbol as shown in FIG. 8A or two symbols as shown in FIG. 8B. And the remaining area not set as the sPDCCH area can be used for the sPDSCH.

As another example, in the case of 7-symbol sTTI, up to 7 symbols can be set in the sPDCCH area.

- Set the frequency domain position of sPDCCH area

It is assumed that the sPDCCH area setting information is basically constructed in the form of FDM / TDM. Basically, the following settings are supported in the sPDCCH area.

■ The sPDCCH area allocation can be set as a continuous area in the frequency domain by default. At this time, the location of the sPDCCH area can be divided into upper, middle, and lower areas as shown in FIG.

Referring to FIG. 9, the sPDCCH region may be continuously set up from RB # 4 to RB # 7 as shown in FIG. 9A, and may be continuously set up from RB # 2 to RB # 5 as shown in FIG. Or may be set consecutively from RB # 0 to RB # 3 as shown in FIG. 9 (c).

Conversely, it is also possible to allocate the sPDCCH area in the distributed form, that is, to allocate the sPDCCH area in which the RBs constituting the sPDCCH area are not continuous with each other. In this case, the allocation pattern of the sPDCCH region must be transmitted to the UE so that the UE can know which RBs are allocated to the sPDCCH region.

Example  1-1. 2- symbol sTTI  If the single symbol / RB (resource block) based sCCE assignment or sCCE  Provide aggregation

In this embodiment, a method of allocating the sPDCCH region in 2-symbol sTTI will be described in detail.

For example, assuming that the sTTI region is set to all 10 PRBs, the sPDCCH region can be allocated to only four PRBs and the remaining six PRBs can be multiplexed by assigning sPDSCHs. According to the present embodiment, since there are control channel elements (CCEs) in units of RBs in the sPDCCH, a total of four sCCEs can exist. Therefore, sPDCCH can support up to four sCCE aggregation levels.

10, the sPDCCH region includes sCCE # 0, sCCE # 1, sCCE # 2 and sCCE # 3 for four RBs from RB # 4 to RB # 7 using only one symbol (Sym.1) SCCEs can be allocated. And the remaining area can be used to transmit the sPDSCH.

Example  1-2. 2- symbol sTTI  In the case of 2- symbol / RB (resource block) based sCCE assignment or sCCE  Provide aggregation

In this embodiment, a method of utilizing the entire 2-symbol allocated to the sPDCCH region in the method of allocating the sPDCCH region in 2-symbol sTTI will be described in detail.

For example, assuming that the sTTI region is set to all 10 PRBs, the sPDCCH region is allocated to only four PRBs and the remaining six PRBs can be multiplexed by assigning sPDSCHs, as in Embodiment 1-1. According to this embodiment, since the control channel element (CCE) is configured in units of RBs in the sPDCCH, four sCCEs can be configured per symbol, and the total of the sCDCCHs constitutes 4 * 2 = 8 sCCEs .

In another configuration method, the sCCE may be configured in units of 2 symbols and 1 RB. At this time, the total number of sCCEs is reduced to 4, but the size of one sCCE is doubled and the number of REs per sCCE is doubled.

11, (a) of FIG. 11 illustrates an example in which the sPDCCH region is composed of four RBs and two symbols, and a CCE is configured in each RB unit of the sPDCCH region, and a total of eight sCCEs ranging from sCCE # 0 to sCCE # Lt; / RTI &gt;

On the other hand, FIG. 11 (b) shows a total of four sCCEs ranging from sCCE # 0 to sCCE # 3 since sCCE is configured in 2-symbol units, and the size of each sCCE is doubled compared to FIG.

Example  1-3. DMRS  density and Regardless of configuration sCCE  Is a single symbol Of RB  Has number of subcarriers

In this embodiment, the basic unit constituting the sCCE will be described. Basically, Legacy RB has 12 subcarriers per single symbol. Also in this embodiment, a system having 12 subcarriers per single symbol is used as it is.

For example, even if two or three of the twelve subcarriers are allocated for DMRS purposes, the number of subcarriers per single symbol does not change to twelve. Only the symbol is excluded from the detection process. As a result, the sCCE can be composed of 10 REs or 10 REs instead of 12 REs (assuming 2 or 3).

Example  2. 7- symbol (Or slot unit) At sTTI sPDCCH  Apply configuration information selectively

In this embodiment, a method of defining sPDCCH in 7-symbol sTTI will be described in detail. The 7-symbol sTTI consists of 7 symbols of one TTI, which is basically the same as one slot unit of the legacy subframe.

Therefore, in the 7-symbol sTTI, the sPDCCH region can be set by the following two methods. First, a method of allocating a sPDCCH region in a distributed form to three or less OFDM symbol regions in the entire frequency band, such as a legacy PDCCH, and a method of allocating an sPDCCH region only in a specific resource region.

According to the present embodiment, when setting the sPDCCH region in 7-symbol sTTI, one of the above two methods can be selectively applied, and the information can be transmitted to the UE through RRC signaling.

The method of allocating only to specific resources is the same as that of the above-described 'Embodiment 1, Embodiment 1-1, Embodiment 1-2, and Embodiment 1-3'. In the case of using the same legacy PDCCH setting, Follow Example 2-1.

Example  2-1. 7- symbol From sTTI  legacy PDCCH  When reusing the allocation method, the number of symbols To the terminal Signaling

Basically, the legacy PDCCH detects the PCFICH to know the number of symbols allocated to the PDCCH. However, if the same structure is applied to the sTTI located in the second slot, the UE must detect the PCFICH again. Therefore, in the present embodiment, the following method is proposed to solve such a problem.

- Method 1: In order to detect the sPDCCH area transmitted in the second slot, the terminal preferentially detects short PCFICH such as legacy PCFICH. This is a method of introducing a new short PCFICH, and the basic principle of short PCFICH reuses the same legacy PCFICH.

- Method 2: The sPDCCH is detected using the predefined number of symbols to detect the sPDCCH area transmitted in the second slot. At this time, the number of symbols of the sPDCCH can be transmitted to the UE through RRC signaling.

Method 3: The sPDCCH region transmitted in the second slot is transmitted based on a single symbol, and the terminal performs sPDCCH detection based on a single symbol. In this case, since the sPDCCH region is previously fixed to a single symbol region, signaling to the UE does not need to be performed.

Example  3. The terminal sPDCCH  Unused resources for detection are used for data transmission

In this embodiment, an operation of transmitting sPDSCH, i.e., data, is performed for a resource for which sPDCCH is not detected among the sPDCCH regions set for detecting the sPDCCH of the UE. At this time, the sTTI areas are orthogonal or different from one another to another.

If the sPDSCH is transmitted to the sPDCCH region in which the sPDCCH is not detected, the resources of the sPDCCH can be utilized efficiently.

For example, referring to FIG. 12, the sPDCCH of the terminal is not detected in the sCCE # 2 and sCCE # 3 in the sPDCCH region. In other words, the resource allocated to the sPDCCH region is not used in the sPDCCH in this case, but becomes empty.

Therefore, the base station can transmit the general data to the mobile station by allocating the corresponding band to the sPDSCH. That is, the base station allocates the sPDSCH to the unused sPDCCH region and transmits the sPDSCH. At this time, the UE can detect its control information in the sPDCCH region first. The UE can detect the detected sPDCCH and perform the data detection based on the assumption that the remaining region in which the sPDCCH is not detected is the sPDSCH.

In this embodiment, a concrete method of setting the sPDCCH area and the multiplexing method of the sPDSCH in the 3GPP LTE / LTE-A system is proposed. The method can be applied to the similar signals and channels as they are, The application is not limited.

13 is a diagram illustrating a configuration of a base station according to the present embodiments.

13, the base station 1300 includes a controller 1310, a transmitter 1320, and a receiver 1330.

The controller 1310 controls the overall operation of the base station 1300 in transmitting a downlink channel in a frame structure of a short transmission time interval required for performing the above-described embodiment. Specifically, the controller 1310 can set information on the sPDCCH area.

At this time, the sPDCCH region may be composed of a single symbol or a plurality of symbols with respect to time as described above. For example, the sPDCCH region may be composed of one or two symbols.

The transmitting unit 1320 and the receiving unit 1330 are used to transmit and receive signals, messages, and data necessary for performing the above-described present invention to and from the terminal.

Specifically, the transmitter 1320 transmits information on the sPDCCH area set by the controller 1310 to the mobile station, and transmits the downlink channel to the mobile station based on the information on the sPDCCH area.

When the transmitter 1320 transmits information on the sPDCCH region to the mobile station, information on the sPDCCH region may be transmitted to the mobile station through RRC signaling.

When a transmission unit 1320 transmits a downlink channel, that is, a downlink control channel or a downlink data channel, to the UE based on the information of the sPDCCH region, a resource not used in the sPDCCH among the resources belonging to the sPDCCH region is re- . In this case, information indicating a resource not used for the sPDCCH can be transmitted to the UE through the DCI.

FIG. 14 is a diagram illustrating a configuration of a user terminal according to the present embodiments.

14, the user terminal 1400 includes a receiving unit 1410, a controller 1420, and a transmitting unit 1430.

The receiving unit 1410 receives downlink control information, data, and messages from the base station through the corresponding channel.

More specifically, the receiver 1410 can receive information on the sPDCCH region from the base station and receive the downlink channel from the base station based on the information on the received sPDCCH region.

At this time, the sPDCCH region may be composed of a single symbol or a plurality of symbols with respect to the time axis as described above. For example, the sPDCCH region may be composed of one or two symbols.

At this time, the user terminal 1400 can receive information on the sPDCCH region from the base station through RRC signaling.

In addition, the controller 1420 controls the overall operation of the user terminal 1400 in response to receiving the downlink channel in the frame structure of the short transmission time interval necessary for performing the above-described embodiment.

Specifically, the controller 1420 can detect downlink control information or downlink data from the downlink channel received from the base station.

When transmitting a downlink channel, that is, a downlink control channel or a downlink data channel, to the UE based on information on the sPDCCH region, a resource not used for the sPDCCH among resources belonging to the sPDCCH region can be reused in the sPDSCH. In this case, information indicating a resource not used in the sPDCCH can be received from the base station via the DCI.

The standard content or standard documents referred to in the above-mentioned embodiments constitute a part of this specification, for the sake of simplicity of description of the specification. Therefore, it is to be understood that the content of the above standard content and portions of the standard documents are added to or contained in the scope of the present invention.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (20)

A method for receiving a downlink channel in a frame structure of a short transmission time interval (sTTI)
Receiving information on a shortened PDCCH (shortened PDCCH) region of a short transmission time interval from a base station; And
And receiving a downlink channel from the base station based on information on the sPDCCH region,
Wherein the short transmission time interval is set to two, three or seven symbols.
The method according to claim 1,
Wherein the sPDCCH region comprises one or two symbols.
The method according to claim 1,
And information on the sPDCCH region is received from the base station through RRC signaling.
The method according to claim 1,
And resources not used for the sPDCCH among the resources belonging to the sPDCCH region are reused for a short data PDSCH (sPDSCH) having a short transmission time interval.
5. The method of claim 4,
And information indicating a resource not used for the sPDCCH is received from the base station through the DCI.
A method for transmitting a downlink channel in a frame structure of a short transmission time interval (sTTI)
Setting information on a downlink control channel (sPDCCH) field of a short transmission time interval;
Transmitting information on the sPDCCH region to a mobile station; And
And transmitting a downlink channel to the UE based on the information on the sPDCCH region.
Wherein the short transmission time interval is set to two, three or seven symbols.
The method according to claim 6,
Wherein the sPDCCH region comprises one or two symbols.
The method according to claim 6,
And transmits information on the sPDCCH region to the MS through RRC signaling.
The method according to claim 6,
And resources not used for the sPDCCH among resources belonging to the sPDCCH region are reused for a shortened PDSCH (sPDSCH) having a short transmission time interval.
10. The method of claim 9,
And transmits information indicating a resource not used for the sPDCCH to the UE through the DCI.
A terminal for receiving a downlink channel in a frame structure of a short transmission time interval (sTTI)
A receiver for receiving information on a downlink control channel (sPDCCH) region of a short transmission time interval from a base station and receiving a downlink channel from the base station based on information on the sPDCCH region;
And a controller for detecting downlink control information or downlink data from the downlink channel,
Wherein the short transmission time interval is set to two, three, or seven symbols.
12. The method of claim 11,
Wherein the sPDCCH region comprises one or two symbols.
12. The method of claim 11,
And information on the sPDCCH region is received from the base station through RRC signaling.
12. The method of claim 11,
And resources not used for the sPDCCH among resources belonging to the sPDCCH region are reused for a short data PDSCH (sPDSCH) having a short transmission time interval.
15. The method of claim 14,
And information indicating a resource not used for the sPDCCH is received from the base station through the DCI.
A base station for transmitting a downlink channel in a frame structure of a short transmission time interval (sTTI)
A controller for setting information on a downlink control channel (sPDCCH) area of a short transmission time interval; And
And a transmitter for transmitting information on the sPDCCH region to a mobile station and transmitting a downlink channel to the mobile station based on information on the sPDCCH region.
Wherein the short transmission time interval is set to two, three or seven symbols.
17. The method of claim 16,
Wherein the sPDCCH region comprises one or two symbols.
17. The method of claim 16,
And transmits information on the sPDCCH region to the MS through RRC signaling.
17. The method of claim 16,
Wherein resources not used for the sPDCCH among resources belonging to the sPDCCH region are reused for a shortened PDSCH (sPDSCH) having a short transmission time interval.
20. The method of claim 19,
And transmits information indicating a resource not used for the sPDCCH to the UE through the DCI.

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